That is what @LlabTooFeR, one of the more well-known smartphone leaksters, claims. He believes that the update is reaching last stages of development as we speak, and should roll out by the end of November/early December. Upgrade to Oreo would be a huge deal, since U11 has been running on 7.1 Nougat since day 1. There are plans to upgrade HTC 10 and U Ultra as well, but we have no details on that.

On the side note, on November 2nd HTC will reveal two variants of the U11, U11 Plus and Lite, with Lite being rumoured to come out with stock Android 8.0.